Infinity Metal Puzzle is a simple, popular and excellent puzzle that has been sold in many forms and quality. It is often found in a collection of several puzzles and made of very light wire to heavy and substantial “stainless” 1/4 inch rod such as this. The concept is the same as in the basic “Twisted Nails” puzzle except that it is a little more challenging and that it has two loops on one of the pieces. It is very strong and won’t be easily damaged but requires no strength to solve, as is normally the case with wire puzzles. It is relatively easy and a good beginner puzzle. You can purchase this puzzle at Puzzle Master.